JPH0748593A - Aqueous cleaning solution - Google Patents

Abstract

(57) [Abstract] [Purpose] A water-based cleaning liquid that can remove oil with a high oil removal rate if it is treated with a high-frequency low-voltage coagulation separator, and that can recover a sufficient degreasing rate for mineral oil stains. provide. [Structure] Processed by a high-frequency low-voltage coagulation / separation device that coagulates and separates oil components by high-frequency low-voltage, mainly contains nonionic surfactant, builder, and rust inhibitor component, and is weakly alkaline or neutral. Aqueous cleaning solution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous cleaning solution for cleaning oil on the surface of an object to be cleaned in the industrial cleaning field.

[0002]

In the field of industrial cleaning, CFCs, 1
-When solvent cleaning is performed using an organic solvent such as 1.1 trichloroethane, it is possible to recycle the organic solvent by the evaporation recovery system due to the nature of the organic solvent. Therefore, in this case, it is possible to run for a long period of time only by replenishing the evaporated organic solvent.

However, in recent years, with the importance of global environmental problems, such organic solvents destroy the ozone layer, and it has been decided to abolish the organic solvents. Therefore, especially in the field of parts cleaning, various changes to alternative cleaning solutions have been made, and aqueous cleaning solutions are being considered as important alternative methods. However, when performing water-based cleaning with such a water-based cleaning liquid, the oil component removed from the object to be cleaned by degreasing is mixed into the water-based cleaning liquid, and the mixed oil component emulsifies the emulsion (O / W type emulsion). Form. In this way, as the water-based cleaning liquid having a higher degreasing rate, the washed oil is more stably emulsified. In a water-based cleaning solution that forms an emulsion, the oil consumes the surfactant to reduce the degreasing rate, and a layer containing a thick emulsion is formed on the surface to re-attach to the object to be cleaned, resulting in a quality after cleaning. Drop it.

Therefore, when the conventional water-based cleaning liquid is used, the water-based cleaning liquid cannot be used for a long period of time as in the case of solvent cleaning, and the water-based cleaning liquid can be used in a relatively short period (1 to 2 weeks). It is necessary to regularly update the entire amount of the water-based cleaning liquid, such as updating it regularly. For this reason, conventionally, for the purpose of separating and removing the emulsified oil from the water-based cleaning liquid to extend the life of the water-based cleaning liquid, each separation device by a filter filtration method, a filter tower separation method, an electrostatic separation method, an overflow circulation method is used. Are also being considered.

[0005]

However, since the conventional water-based cleaning liquid has been studied as a single substance, that is, it is necessary for the degreasing rate to be exhibited with respect to the water-based cleaning liquid which only plays a part of the cleaning work. Since it was responsible for all of the work, there is a secondary treatment regarding wastewater treatment (high oil removal rate) and work safety (danger due to strong alkalis), which is contrary to the cleaning action by chemical components. It was

Further, conventional separation devices have also been studied as a single unit, and as a result, oil content can be removed but the degreasing rate is lowered, or the degreasing rate is good but the oil content is not sufficiently removed. There were things or short ones. Both separators rely on natural separation of oil, and were developed in terms of how efficiently the once separated oil is removed from the system, taking into consideration how to effectively destroy the emulsion. Not not.

Further, for industrial use, especially for removing mineral oil stains such as cutting oil, rust preventive oil and press oil with a high degreasing rate, it is effective to employ a nonionic surfactant. Therefore, although a high oil removal rate is desired for a water-based cleaning liquid that employs a nonionic surfactant, if such a water-based cleaning agent is treated with a conventional separation device,
In the method of adding a polyvalent ionic substance to a polar group as in the case of treating an aqueous cleaning solution that uses an anionic / cationic surfactant, the surfactant itself does not have a polar group, so the emulsion Cannot be effectively destroyed.
Further, the nonionic surfactant has a large molecular weight as compared with the anionic / cationic surfactant, and has a heavy burden in terms of BOD (biochemical oxygen demand) and COD (scientific oxygen demand).

Therefore, in the conventional separation apparatus, the effect of breaking the emulsion cannot be sufficiently obtained with respect to the water-based cleaning liquid employing the nonionic surfactant, and the oil is removed at a satisfactory high oil removal rate. I can't. Therefore, in the combination of the conventional water-based cleaning liquid and the conventional separator, the degreasing rate and the oil removal rate for mineral oil stains cannot both be achieved, and the water-based cleaning solution cannot run for a long period of time. It was supposed to cause the deterioration of the environment.

Therefore, the present applicant has filed Japanese Patent Application Laid-Open No. 4-5900.
In JP-A-2, a high-frequency low-voltage coagulation / separation device for aggregating and separating oil by high-frequency low-voltage was proposed, and an aqueous cleaning solution most suitable for such a high-frequency low-voltage coagulation / separation device was studied. That is, the present invention has been made in view of the above-mentioned conventional circumstances, and when treated with a high-frequency low-voltage coagulation separation device, it is possible to remove oil with a high oil removal rate, and this is sufficient for mineral oil stains. It is an object to provide an aqueous cleaning liquid capable of recovering the degreasing rate.

[0010]

The inventors of the present invention have investigated the ionicity of the surfactant in various water-based cleaning liquids for the above-mentioned purpose. It has been discovered that a difficult aqueous cleaning solution is a combination of nonionic and anionic surfactants.

Based on this knowledge, the degreasing rate and the tendency of the oil removal rate by the high-frequency low-voltage coagulation separation device regarding the molecular structure of the surfactant, the builder and the additive to be mixed in the aqueous cleaning solution were grasped, and as a result, The present invention has been completed by discovering a water-based cleaning liquid capable of maintaining a long life by a high-frequency low-voltage coagulation separation device without lowering the rate.

That is, the aqueous cleaning solution of the present invention is treated by a high-frequency low-voltage coagulation / separation device for aggregating and separating oil by high-frequency low-voltage, and mainly comprises a nonionic surfactant, a builder, and a rust preventive component. And is weakly alkaline or neutral. The conventional water-based cleaning liquid and the water-based cleaning liquid of the present invention are completely different in terms of the requirement for the water-based cleaning liquid. In other words, conventionally, the water-based cleaning liquid was responsible for all of the degreasing rate, and the degreasing rate was pursued even if the wastewater processability and handling danger were neglected. From the viewpoint of maintaining and improving the environment and working environment, it is required that the degreasing rate be shared by the water-based cleaning liquid, the cleaning device, the auxiliary equipment, etc., and the water-based cleaning liquid be developed so that the wastewater treatment property is emphasized as much as possible.

Therefore, the inventors of the present invention have considered the point of how to efficiently break the emulsion together with the development of the high-frequency low-voltage coagulation / separation device. The aqueous cleaning solution of the invention was developed. [1] High-frequency low-voltage flocculation / separation device As a high-frequency low-voltage flocculation / separation device, JP-A-4-5900
The one described in Japanese Patent No. 2 can be adopted. [2] Surfactant When an anionic / cationic surfactant is used in the water-based cleaning liquid of the present invention, the emulsion is less likely to be broken and the efficiency is poor during treatment because of high conductivity.
Therefore, nonionic surfactants are mainly used.

In the aqueous cleaning solution of the present invention, it is preferable to employ a surfactant in which the hydrophobic group is located at the end of the molecule and the hydrophilic group is located in the center of the molecule. Certainly, surfactants include hydrophilic group-hydrophobic group type, hydrophilic group-hydrophobic group-hydrophilic group type, and hydrophobic group-hydrophilic group-hydrophobic group type, both of which have a hydrophobic group or a hydrophilic group. When both sides are surrounded by different groups, the effect of each group cannot be sufficiently obtained, and the solubilizing / emulsifying effect is reduced. In the aqueous cleaning solution of the present invention, if the and surfactants are used, the solubilization / emulsification effect is reduced during degreasing, but the oil content is easily removed during the treatment.

Further, in Table 1, HLB (hydrophobic-lipophilic ba of the surfactant) necessary for emulsifying the representative oils is shown.
Lance); in the case of an ethylene oxide nonionic surfactant, the weight fraction of the polyethylene glycol portion in the surfactant is 1/5). In the water-based cleaning liquid of the present invention, as shown in Table 1, it is possible to select an appropriate value of HLB10 to 14 for mineral oil, and to lower HL when animal and vegetable oils are mixed in addition to mineral oil.
B can be selected.

[0016]

[Table 1] On the other hand, in conventional water-based cleaning liquids, HLB does not place importance on wastewater treatment for environmental protection, but rather pursues a cleaning action to increase the degreasing rate, and therefore a formulation that maximizes emulsion stability is prepared. There is. That is, in order to improve the degreasing rate of the aqueous cleaning liquid, as a surfactant,
HLB that is most suitable for emulsification of oils in order to increase the stability of the solubilized / emulsified product formed in the washing process,
And, a structure in which an aliphatic hydrocarbon and an aromatic hydrocarbon are located at the terminal, in which the structure of the hydrophobic group is based on mineral oil, is used, and the hydrophobic group is usually an alkyl group having 18 to 20 carbon atoms, Alkylphenols with C8-C9 alkyl have been used. And solubilization of oil
In order to secure an increase in the emulsified amount, the blending ratio of these surfactants was increased, and about 10 g / L was used as a nonionic surfactant in the used state.

That is, the following can be adopted as the surfactant in the aqueous cleaning solution of the present invention. (1) Examples of the nonionic surfactant having an excellent oil removal rate include ethylene, a nonionic surfactant in which a hydrophilic group is located near the center of a branched hydrophobic group such as a polyethylene oxide adduct of a higher secondary alcohol, ethylene. Oxide (E
O) -Propylene oxide (PO) addition type nonionic surfactant, which is a nonionic surfactant in which a polyethylene oxide hydrophilic group is located between a hydrophobic carbon chain and a polypropylene oxide group, Pluronic Type nonionic surfactant having a hydrophobic group sandwiched between two or more hydrophilic groups, and a pluronic type nonionic surfactant having a hydrophobic carbon chain A nonionic surfactant containing one or more double bonds can be adopted.

However, among these nonionic surfactants, those having a carbon chain as a hydrophobic group are those having a carbon chain number of C ₈ to
And _22, C ₁₂ ~ ₁₈ is preferable Speaking further. The number of moles of ethylene oxide added to the hydrophilic group of these nonionic surfactants is preferably 10 to 20 moles. The above are surfactants for ensuring the oil removal rate.

(2) In contrast to the above, it is possible to employ a nonionic surfactant of a type that improves the degreasing rate and does not hinder the oil removal rate. Examples thereof include polyoxyethylene-added higher alcohol ethers, polyoxyethylene-added alkylphenol ethers, polyoxyethylene-added alkylamines, polyoxyethylene-added alkylamides, and polyoxyethylene adducts of tween-type sorbitan fatty acid esters. . For the oil removal rate, the more the number of addition moles of ethylene oxide is, the better, but for the degreasing rate, the smaller the number of addition moles is, the better. Therefore, the addition mole number is 10 to 20. Can be used. Further, the hydrophobic group carbon chains of these nonionic surface active agent is a _{C 8 ~ 22, C 12 ~} 18 Still more desirable.

(3) The weight ratio when the above two kinds of nonionic surfactants are combined is the same as that of the former (1).
The latter (2) type has a ratio of 50/50 to 95/5, preferably 65/35 to 93/7, to secure the oil removal rate by the high-frequency low-voltage coagulation separator. The ratio of the nonionic surfactant of the type (2) is 50 weight (wt).
%, The emulsion stability becomes large and it becomes difficult to improve the oil removal rate. When the ratio of the nonionic surfactant of the type (1) is 95 wt% or more, the oil removal rate improves. Is not desirable because it causes degreasing rate.

The blending ratio of the nonionic surfactant (1) and (2) in the cleaning liquid formulation is preferably 0.5 to 7 g / L, and more preferably 1 to 6 g.
/ L. If it is 0.5 g / L or less, the degreasing rate cannot be expected to be maintained, and if it is 7 g / L or more, the emulsion stability in the cleaning liquid formulation increases and a problem occurs in the oil removal rate, which is not desirable.

In the aqueous cleaning solution of the present invention, if necessary,
In order to enhance the natural separability of the oil component, for example, a cationic surfactant such as an alkylmethylammonium type surfactant may be added to the cleaning liquid formulation within 1 wt%. [3] Builder The force of the aqueous cleaning solution is not established only by the surfactant, and the effect of the builder that supports the effect of the surfactant cannot be ignored.

The effect of the builder is that it mainly adsorbs to solid and liquid particles in an aqueous cleaning solution to change the surface potential, or is originally effective for the solubility of a surfactant which is not completely dissolved in an aqueous solution. Therefore, the presence of a builder that is an inorganic or organic salt that has ionicity and is superior in solubility limits the solubility of the surfactant, and individual molecules of the surfactant are present in the aqueous cleaning solution. Instead, it forces the formation of aggregates of surfactant molecules called micelles.

This effect is stronger as the builder is more alkaline, but in the past, on the contrary, the nonionic surfactant was not stable in the aqueous cleaning solution, and the anionic surfactant more stable in alkali was used. Was used in combination to stabilize the nonionic surfactant. In addition, when the alkalinity of the water-based cleaning liquid becomes strong, the surface charges increase due to the adsorption of alkaline anions on the emulsion particles and solid particles in the water-based cleaning liquid, the dispersion is stabilized, and the oil removal rate decreases.

Therefore, the aqueous cleaning solution of the present invention employs a low-alkali or neutral builder which holds PH around neutral. (1) As the inorganic builder, sodium or potassium salt of tertiary phosphoric acid, sodium salt or potassium salt of phosphoric acid-hydrogen, sodium salt or potassium salt of pyrophosphoric acid, sodium salt or potassium salt of tripolyphosphoric acid, sodium carbonate salt A weakly alkaline to neutral salt such as a salt or potassium salt, a sodium salt or potassium salt of bicarbonate, a sodium salt or potassium salt of sulfuric acid can be used.

Even if a strong alkali such as caustic soda or caustic potash is used for pH adjustment, addition of a large amount thereof hinders the oil removal rate. (2) Organic builders include gluconic acid, oxalic acid,
Hydroxyacetic acid, lactic acid, malonic acid, citric acid, tartaric acid,
Malic acid, succinic acid, etc. can be adopted. Also,
It is also possible to employ these salts (sodium salt, potassium salt, ammonium salt, etc.). Of these salts,
Ammonium salts can include ammonium salts of organic amines such as mono-, di-, tri-ethanolamine.

As an aqueous cleaning solution, when considering the impact on the environment in the future, phosphate as an inorganic builder, especially sodium tripolyphosphate (STPP) is excellent in oil removal rate and degreasing rate, but in rivers, lakes and marshes. Causes eutrophication of sea areas. Therefore, it is considered that organic carboxylic acid salts as an organic builder will be desirable as a builder in the future.

As the builder, a single composition is selected from each of the inorganic builder and the organic builder, and a plurality of compositions are selected from each of the inorganic builder and the organic builder. And a plurality of compositions from organic builders can be used in combination. And the compounding ratio of the builder in the cleaning liquid composition (referred to as the composition before being made into an aqueous solution. The same applies hereinafter) is 0.5 to 20 g / L (L is the entire volume (liter). The same applies hereinafter. ), Desirably 1 to 15 g / L. When the lower limit is less than 0.5 g / L, a supporting effect for washing as a builder cannot be obtained, and an effect on oil removal rate is hardly obtained. When the upper limit is 20 g / L or more, although depending on the composition of the builder, there is a problem in solubility, which is not desirable from the viewpoint of stability of properties of the cleaning liquid formulation. [4] Anti-corrosion agent component In order to switch from solvent cleaning to water-based cleaning, the cleaning liquid composition has an anti-corrosion effect such as a mono-molecular adsorption film of an organic solvent formed on the surface of the object to be cleaned by solvent cleaning. It is necessary to positively add it by adding the agent component.

For this purpose, organic amines such as morpholine, N-methyl-morpholine and N-ethyl-morpholine can be used. As a result of investigating the correlation between these rust preventive components and the compounding ratio, and the oil removal rate by the high-frequency low-voltage coagulation separation device, the rust preventive components were suppressed as much as possible within the range where the rust preventing effect was obtained It was found that the oil removal rate was not impaired, but the oil removal rate was lowered when it was added in an amount equal to or more than the surfactant in the cleaning liquid formulation.

Therefore, the mixing ratio of the rust preventive component in the cleaning liquid composition must be equal to or less than the mixing ratio of the surfactant (mixing ratio: 0.5 to 20 g / L, preferably 1 to 15 g). / L) is preferred. If it is 0.5 g / L or less, the rust preventive effect cannot be obtained when the object to be cleaned is left standing. [5] PH of aqueous cleaning solution In the present invention, when an organic acid is used as a builder and an organic amine is used as a rust preventive component, it is necessary to finally adjust the aqueous cleaning solution to a pH suitable for degreasing rate and oil removal rate. There is.

Therefore, for fine adjustment of the PH, the PH decreasing component such as the organic acid or neutral salt having acidic hydrogen as a builder and the PH increasing component such as caustic alkali, weak alkali or organic amines as described above are used. Used to bring the pH of the wash liquor formulation to 8-9.5. The oil removal rate should be as low as possible within this range. The cleaning liquid composition thus obtained has a concentration of 5 to 300 ml / L, preferably 1 when used.
An aqueous cleaning solution is prepared by preparing an aqueous solution of 0 to 200 ml / L. This aqueous cleaning solution is at room temperature to 8
Dipping, spraying at 0 ° C, preferably 40-60 ° C
The object to be cleaned can be washed by a washing method such as pouring or brushing. When cleaning by spray method,
A pump pressure of 0.1 to 10 kg / cm ² can be applied.

After washing with this water-based washing liquid, the article to be washed may be naturally dried without washing with water, washed with water to move to the next step, or forcedly dried after washing with water. The cleaning process for cleaning an object to be cleaned with an aqueous cleaning liquid involves some surface chemical phenomena, but if it is considered very simply, it will be as follows. First, when the water-based cleaning liquid comes into contact with the surface of the object to be cleaned which is covered with oil stains in the water-based cleaning liquid, the surface does not get wet only with water, but in the case of the water-based cleaning liquid, the surface of the object to be cleaned gets wet.
Here, while the interfacial tension of oil and water is greatly different,
The addition of surfactant reduces the interfacial tension of water. In this case, the effect of the surfactant is enhanced by using together an inorganic salt or an organic salt called a builder, rather than using the surfactant alone.

Subsequent to the wetting phenomenon of the oil stain surface, the process in which the water-based cleaning liquid penetrates into the oil stain, the solubilization phenomenon of incorporating the oil stain into the micelle formed by the surfactant on the oil surface, and the large oil stain. A surfactant molecule surrounds the hydrophobic group on the oil side and the hydrophilic group on the water side to surround it, causing an emulsification phenomenon that disperses oil lumps and separates oil stains from the surface of the object to be washed. .

[0034]

【Example】

(Example 1) A cleaning liquid formulation having the following formulation was prepared, and the oil removal rate and the degreasing rate were evaluated by a test device having the same principle as the high frequency low voltage coagulation separation device. In addition, all the following compounding ratios are wt%.

[Cleaning liquid formulation] Oleyl alcohol polyoxyethylene (15 mol) adduct 2% Secondary linear alcohol polyexethylene (HLB16) adduct 0.5% Nonylphenol polyoxyethylene (15 mol) adduct 0 0.5% polyoxypropylene-polyoxyethylene-block polymer 2.5% gluconic acid 3% oxalic acid 1.5% morpholine 2% water balance Using the above washing liquid formulation, mix with water at a concentration of 50 ml / L, An aqueous cleaning solution was prepared.

[Evaluation of Oil Removal Rate] The above water-based cleaning liquid 400
0.1% of quenching oil was added to ml, and the mixture was forcibly stirred and mixed for 5 minutes using a tabletop mixer. This was introduced into the beaker of the test equipment and the electrodes were operated at 60 KHz, 3.5 V,
It was energized at 1.2 A and treated for 20 minutes. It is to be noted that FIG. 1 shows a photomicrograph of the water-based cleaning liquid before voltage application, and FIG. 2 shows a photomicrograph of the water-based cleaning liquid during voltage application. 1 and 2
From this, it can be seen that the emulsion particles are dispersed before the voltage is applied and the emulsion particles are aggregated in the application direction during the voltage application. The treated water-based cleaning liquid was sampled from the bottom of the beaker, and the residual oil concentration was measured according to JIS-K-0.
It was evaluated based on 102 n-hexane extract substance measurement method. As a result, an oil removal rate of about 65% was obtained.

[Evaluation of Degreasing Rate] A cold rolled steel sheet coated with quenching oil was baked in an oven at 120 ° C. for 30 minutes to obtain a test piece. This test piece was subjected to spray cleaning with a water-based cleaning solution after treatment. The conditions for spray cleaning are 60 ° C., spray pressure: 2 kg / cm ² , and 2 minutes. The degreasing rate was represented by the water-wetted area rate by visual observation in the water washing step after spray washing. As a result,
A degreasing rate of 100% was obtained. (Example 2) A cleaning liquid composition having the following composition was prepared in the same manner as in Example 1, and the oil removal rate and the degreasing rate were evaluated by the same test apparatus as in Example 1.

[Cleaning liquid formulation] Higher alcohol polyoxyethylene (9 mol) polyoxy propylene (5 mol) adduct 2% polyoxyethylene secondary linear alcohol ether (HLB13.5) 1.5% lauryl alcohol polyoxy Ethylene (20 mol) adduct 0.5% polyoxypropylene-polyoxyethylene-block polymer 1.5% sodium tripolyphosphate 9% citric acid 1.5% N-methyl-morpholine 2% water balance balance of the above washing liquid It was mixed with water at a concentration of 50 ml / L to prepare an aqueous cleaning solution.

[Evaluation of Oil Removal Rate] The oil removal rate was 75%. [Evaluation of Degreasing Rate] The degreasing rate was 75%, and the degreasing rate was at a level at which there was no practical problem. (Example 3) A cleaning liquid composition having the following composition was prepared in the same manner as in Example 1, and the oil removal rate and the degreasing rate were evaluated by the same test apparatus as in Example 1.

[Cleaning liquid formulation] Oleyl alcohol polyoxyethylene (10 mol) adduct 0.5% Secondary linear alcohol polyexyethylene adduct (HLB16) 2% Nonylphenol polyoxyethylene (15 mol) adduct 0 0.5% polyoxypropylene-polyoxyethylene-block polymer 2.5% gluconic acid 3% oxalic acid 1.5% morpholine 2% water balance Using the above washing liquid formulation, mix with water at a concentration of 50 ml / L, An aqueous cleaning solution was prepared.

[Evaluation of Oil Removal Rate] The oil removal rate was about 50%, and there was almost no decrease in the oil removal rate compared to 65% in Example 1. [Evaluation of Degreasing Rate] The degreasing rate was 100%, which was the same as in Example 1 in terms of degreasing rate. (Comparative Example 1) A cleaning liquid formulation having the following formulation was prepared in the same manner as in Example 1, and the oil removal rate and the degreasing rate were evaluated by the same test apparatus as in Example 1.

[Cleaning liquid formulation] Nonylphenol polyoxyethylene (15 mol) adduct 8% Polyoxypropylene-polyoxyethylene-block polymer 3.5% Caustic soda 3% Morpholine 2% Water balance 50 ml using the above cleaning liquid formulation An aqueous cleaning solution was prepared by mixing with water at a concentration of / L.

[Evaluation of Oil Removal Rate] The oil removal rate was about 30%, and no significant effect was obtained as compared with Example 1. [Evaluation of Degreasing Rate] The degreasing rate was 85%, which was a practically acceptable level in terms of degreasing rate. (Comparative Example 2) A cleaning liquid composition having the following composition was prepared in the same manner as in Example 1 except that the mixing ratio of the rust preventive component was equal to or more than the mixing ratio of the surfactant. The oil removal rate and the degreasing rate were evaluated by the test device.

[Cleaning liquid formulation] Oleyl alcohol polyoxyethylene (15 mol) adduct 2% Secondary linear alcohol polyexethylene ethylene adduct (HLB16) 0.5% Nonylphenol polyoxyethylene (15 mol) adduct 0 0.5% polyoxypropylene-polyoxyethylene-block polymer 2.5% gluconic acid 3% oxalic acid 1.5% morpholine 11% water balance Using the above washing liquid formulation, mix with water at a concentration of 50 ml / L, An aqueous cleaning solution was prepared.

[Evaluation of Oil Removal Rate] The oil removal rate was about 41%, and it was recognized that the oil removal rate was lower than the oil removal rate of 65% in Example 1. [Evaluation of Degreasing Rate] The degreasing rate was 100%, which was the same as in Example 1 in terms of degreasing rate.

Therefore, it can be seen that the aqueous cleaning liquids of Examples 1 to 3 can remove the oil content with a higher oil removal rate than those of Comparative Examples 1 and 2 and thereby recover a sufficient degreasing rate for mineral oil stains. . (Test) The high-frequency low-voltage coagulation separation device shown in FIG. 3 is prepared. In this separator, the reaction container 1 and the recovery container 2 are connected at the lower end, and a plurality of electrode plates 3 are vertically arranged inside the reaction container 1 alternately with a plurality of inner walls 1a of the reaction container 1. It is set up. The inner wall 1a of the reaction vessel 1 and the electrode plate 3 are connected to an AC power source 4, and a predetermined high frequency low voltage is applied between the inner wall 1a of the reaction vessel 1 and the electrode plate 3 by energization of the AC power source 4. It is done like this. Also, the reaction container 1
An oil discharge passage 1b is opened above the cleaning container 2, and a cleaning liquid recovery passage 2b is opened above the recovery container 2.

The aqueous cleaning liquid containing oil is introduced into the reaction vessel 1 from the lower end, and the emulsion containing oil is aggregated in the reaction vessel 1. Agglomerated emulsion is the reaction vessel 1
And is discharged to the outside from the oil discharge passage 1b. In addition, the water-based cleaning liquid from which oil has been removed is collected in the recovery container 2
Through the cleaning liquid recovery passage 2b to the outside. The water-based cleaning liquids of Example 1 and Comparative Example 1 were used to evaluate the degreasing rate of gears to which the quenching oil had adhered and the oil removal rate of the quenching oil mixed in by the high-frequency low-voltage coagulation separator.

[Evaluation of Degreasing Rate] The quenching oil-attached gear was washed by spray washing. The conditions for spray cleaning are: temperature: 60 ° C., time: 8 minutes, spray pressure: 2 kg / c
m ² , water-based cleaning liquid amount: 200 L. After washing with water and drying,
The residual oil was extracted with tetrachlorohydrocarbon and then measured with an infrared absorption type oil removal rate measuring device. As a result, the amount of oil adhered before cleaning was 5 g per gear, but both the aqueous cleaning liquids of Example 1 and Comparative Example 1 were 12 to 17 mg after cleaning.
And the degreasing rate was good.

[Evaluation of Oil Removal Rate] Example 1 and Comparative Example 1
Using 200 liters of the water-based cleaning liquid of Example 1, 800 gears to which quenching oil had adhered were washed for 24 hours while removing oil from the above high-frequency low-voltage coagulation / separation device under the same energization conditions as in Example 1 and the like. The results are shown in Fig. 4. The oil content in the water-based cleaning liquid after 24 hours was about 1.5 wt% in Comparative Example 1, while it was 0.2 wt% or less in Example 1, and the oil content removal ratio of the water-based cleaning liquid in Example 1 was The advantage of was clear.

[0050]

As described above in detail, since the aqueous cleaning solution of the present invention has the constitution described in the claims, it is possible to obtain a high oil removal rate if it is processed by the high frequency low voltage coagulation separation device. The oil content can be removed, and thus a sufficient degreasing rate for mineral oil stains can be restored.

Therefore, if this water-based cleaning liquid is used together with a high-frequency low-voltage coagulation separation device, both the degreasing rate for mineral oil stains and the oil removal rate can be made compatible, so that the water-based cleaning solution can be run for a long period of time and the global environment can be maintained. And, it becomes possible to maintain a good working environment.

[Brief description of drawings]

FIG. 1 shows a particle structure of an aqueous cleaning liquid before voltage application 40
It is a 0X micrograph.

FIG. 2 shows a particle structure of an aqueous cleaning liquid under voltage application.
It is a 0X micrograph.

FIG. 3 is a schematic cross-sectional view of a high-frequency low-voltage coagulation separation device used in the test.

FIG. 4 is a graph showing an oil content ratio in an aqueous cleaning liquid of Example 1 and Comparative Example 1 in a test.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masao Inuzuka 50 Noda Machibawari, Kariya City, Aichi Prefecture Yuken Industry Co., Ltd. (72) Inventor Fumio Kawahara 7-16-1 Kakimoto Town, Toyota City, Aichi Prefecture MEC Co., Ltd. Within International

Claims (1)

[Claims] 1. A high-frequency low-voltage coagulation / separation device that coagulates and separates oil components by high-frequency low-voltage and mainly contains a nonionic surfactant, a builder, and a rust preventive component, and a weak alkali or An aqueous cleaning solution characterized by being neutral.